Taxonomic phylum
= Taxonomic phylum
A <taxonomic phylum> is a major <taxonomic rank> conventionally below a <taxonomic kingdom> and above a <taxonomic class>. A particular phylum is a <taxon> at that rank. For example, <chordates> form the phylum containing <Mammalia>, which in turn contains orders such as <Carnivora>.<Biology 2e by Mary Ann Clark and others>[section 20.1, Classification Levels and Figures 20.5–20.6]{ref}
The same animal can consequently belong to a phylum, a class and an order without these being competing identifications. Each level adds information about nested membership. The rank word phylum identifies a position in the hierarchy; the group name identifies which <taxon> occupies that position.
For a constructed survey example, suppose one phylum is represented by four sampled classes with 3, 7, 2 and 8 sampled <species>. Its total is $3+7+2+8=20$. A second phylum with two sampled classes containing ten species each has the same total. Reporting only twenty species for each phylum loses the class-level distribution, and neither count establishes the total diversity of the unsampled phylum.
A <taxonomic rank> does not itself specify a fixed age, number of constituent groups or numerical genetic distance. A <phylogenetic tree> addresses evolutionary relationships, while ranked names select particular groupings for classification.<Biology 2e by Mary Ann Clark and others>[section 20.1, Phylogenetic Trees and Classification Levels]{ref} The usefulness of the rank comes from organizing comparisons; the scientific interpretation still depends on what was sampled and the evidence supporting membership.